The present invention relates generally to the field of engine systems having valve trains capable of being deactivated hydraulically. It finds particular application in conjunction with deactivating roller followers used to deactivate individual valves in an internal combustion engine and will be described with particular reference thereto. It will be appreciated, however, that the invention is also amenable to other like applications.
Deactivating rocker arm assemblies are generally known in the art for their use in internal combustion engines and are typically used to deactivate exhaust and intake valves. This is done as part of an overall strategy to selectively deactivate one or more combustion chambers (or cylinders) of the engine to conserve fuel during idle or low load conditions. Combined with the primary benefit of not consuming fuel in the deactivated cylinders, deactivating the valves further enhances efficiency by preventing the pistons of the deactivated cylinders from using engine power to pump air through the engine.
However, a common problem involves the reliability of known deactivating rocker arm assemblies to consistently activate or deactivate a given valve upon demand. The root cause of these failures typically involve the latching components that are responsible for engaging an oscillating finger, lever, or arm and transmitting the high load forces generated by a rotating cam lobe to the stem of a valve. In some cases, the failure can be attributed to a misalignment of the latching components which inhibit positive engagement between the oscillating arm and the stationary latch of the rocker arm. Poor alignment can result from an inadequate design, poor manufacturing tolerance, and or long term wear.
Another common problem involves the manufacturability of known deactivating rocker arm assemblies. Often, the oscillating arm and other components require several machining steps (drilling, milling, grinding, turning etc.) before they can be assembled as a finished product. These additional steps increase the overall cost of the product as well the likelihood of manufacturing defects.
For these reasons, a need exists to provide an improved deactivating roller finger follower or rocker arm assembly that reduces misalignment of the latching components, decreases latch loads and associated wear while being cost effective to manufacture.